I did look and I did understand. Do you know what the unclaimed payment in paypal is? That's when payment is sent and the person who receives it doesn't claim/accept the payment.
How can the item be lost, they wouldn't even have sent it out unless they had accepted the payment. I'm sure you wouldn't post an item out to anyone unless you have confirmed that payment is completed and you have the money in your account. Because if payment is left unclaimed, the item is sent and you receive the item, you can go back and reverse your payment as it is unclaimed and you will essentially have an item for free.
Lack of communication or NO communication is reason enough for the negative feedback especially when your item doesn't arrive, you have paid for it and on top of that you are trying to communicate and find out what could have happened with no response.
The 99p part...it could be a £300 part, still no excuse for no communication even if item has gone missing. The rest are indeed fine.